Collection of waste heat passing upwardly in a metal stack, or in a brick chimney has long been proposed, but such structures do not appear to have come into general use.
In U.S. Pat. No. 866,842 to Comstock of Sept. 24, 1902 a metal stack is disclosed which extends from cellar to roof in a building and both the furnace and stack are provided with an exterior liquid jacket, the return pipes requiring holes in the floor.
In U.S. Pat. No. 2,307,600 to Munters of Jan. 5, 1943, a similar jacketed metal stack is disclosed extending from cellar to roof, with return pipes also requiring holes in the floors. The jacketed metal stack is in a plurality of sections coupled end to end and a built in superstructure is required to install and support the device.
It has also been proposed to incorporate a full length, or a sectional heat exchanger in an existing chimney of a building.
Exemplary of such systems in U.S. Pat. No. 2,524,843 to Slifer of Oct. 10, 1950, wherein the brick chimney encloses a central vertical smoke flue for the combustion gases, and surrounded by a pair of concentric air flues which feed heated air through holes in the walls into the building.
Also proposing such a system within a brick chimney is the circulator of U.S. Pat. No. 1,984,949 to Smith of Dec. 18, 1934, wherein the brick chimney also encloses a central vertical smoke flue for the combustion gases, encompassed by a fresh air passage which connects with holes in the walls of the building. The central smoke flue is in sections, connected end to end and is provided with horizontal fins. Like the Munters sectional metal stack of U.S. Pat. No. 2,307,600, which is built into the building, the Smith sectional stack is built into the inside of the chimney and supported on cross plates embedded in the brick work.